Influence of nitrogen supply on micropropagation and subsequent microtuberization of four potato cullwars

A medium containing low amounts of nitrogen (19–23 meq.l^?1) produced optimum results in micropropagation as revealed by the number of nodes, internode length, chlorophyll content, and leaf area of four potato cvs. belonging each to four different maturity groups. Decreasing amounts of nitrogen also increased chlorophyll content in all four cultivars tested. The NH ₄ ⁺ concentration did not have an effect on micropropagation for low nitrogen supplies. In all cvs., except Baraka, there was a “carry over” effect of the nitrogen content in the micropropagation medium onto subsequent tuberization, the lower nitrogen (23 meq.l^?1) advancing tuber initiation. Microtuberization of cv. Jaerla was earlier in darkness than under short days regardless of the propagation medium used.